The production of refinery products such as the various oil fractions, fuels and solvents involve the preheating of crude oils to from 150.degree. C. to 350.degree. C. prior to distillation into various fractions and followed by subsequent exposure of some fractions to higher temperatures of 350.degree. C. to 700.degree. C. As an illustration most of the gasoline produced today is obtained by the thermal or catalytic cracking of heavier petroleum hydrocarbon feed stocks such as light or heavy gas oils, cycle stocks, virgin or topped crude oils, lube stocks, kerosene, and kerosene-gas oil mixtures. A number of different thermal and/or catalytic cracking processes known in the petroleum industry under designations such as Fluid Process, Thermofor, Houdry, Platforming, Thermal Reforming, Viscosity-Breaking, etc., are employed for the purpose. Although these various processes differ considerably as to the precise manner in which the heavier hydrocarbon molecules are cracked to yield gasoline, they all involve the heating of the hydrocarbon feed stock to a high temperature (150.degree.-370.degree. C.) and the passage of such heated stock, optionally mixed with a cracking catalyst, through heated tubes, reactors, convertors, and tower stills.
Regardless of the refinery process used, the distillation and/or cracking operation (particularly the former) always results in the formation of undesirable carbonaceous material which accumulates on the inner surfaces of the preheating and/or cracking unit to lower its efficiency at which time the unit must be dismantled, cleaned, and reassembled. Of course, such cleaning operations are not only tedious and costly, but result in a large proportion of "down-time" during which the unit is not functioning. One approach to antifoulant processes is set forth in U.S. Re. No. 26,330 wherein deposit formation in refinery units is inhibited by incorporating in the feed stock a small percentage (usually about 0.0012-0.04 weight percent) of an acylated amine prepared by reacting a hydrocarbon-substituted succinic acid with an alkylene amine.
Another approach to the prevention of fouling of process equipment by an oil stream in refinery operations is to incorporate in the feed 0.001 to 2 wt. % of a bis-oxazoline reaction product of polyisobutenylsuccinic anhydride with a 2,2 disubstituted-2-amino-1-alkanol, such as tris-hydroxy methylaminomethane (see U.S. Pat. No. 4,195,976).
It is, therefore, an object of the present invention to inhibit the accumulation of harmful carbonaceous material on the inner surfaces of vessels confining a heated hydrocarbon fluid.
Another object is to disperse the carbonaceous material formed during the preheating of a crude oil and thereby inhibit its accumulation on the various parts of the inner wall of the heat exchanger prior to its introduction into the distillation unit, e.g. a pipe still.
Yet another object is to reduce the amount of downtime in the operation of refinery heat exchangers and cracking units.